Microphysical Process Variability within Taiwan's Mei-Yu and Non-Mei-Yu Storms

Extreme rainfall occurs around the world with major impacts such as flooding and mudslides. Due to the extreme rainfall proving to be difficult to forecast, understanding why and how these storms work is an important step towards clarity. This study analyzes heavy rainfall-producing storms occurring in mountainous Taiwan as part of the Prediction of Rainfall Extremes Campaign in the Pacific (PRECIP) during May-August 2022. Considering the Mei-Yu front, the quasi-stationary boundary in moisture and winds that leads to extreme rainfall over this region, we investigated whether there is a relation between the precipitation processes of two types of storms (Mei-Yu and non-Mei-Yu), with respect to terrain elevation (specifically coast vs. mountains). Using S-POL dual-polarization radar data retrieved on the northwest coast of Taiwan, our results showed distinct variability in precipitation processes between the storm type and terrain elevation. A Mei-Yu storm over the coast primarily featured coalescence processes with little temporal and spatial variability throughout; however when it was over the mountains, the variability was quite drastic, yet still primarily featuring coalescence processes. The Non-Mei-yu case was an afternoon thunderstorm that brewed over the mountains, showing the most variability in time and space, but drop breakup processes were dominant. This analysis highlights differences in ice-phase versus warm-rain processes. Specifically, ice-phase processes had more of an influence in the non-Mei-Yu storm than the other two Mei-yu cases.